Cancer and Obesity

What is Known About the Relationship Between Obesity and Cancer?

Obesity is strongly associated with an increased risk of several cancers, including:

  • Esophageal adenocarcinoma
  • Pancreatic cancer
  • Colorectal cancer
  • Postmenopausal breast cancer
  • Endometrial (uterine) cancer
  • Kidney cancer
  • Thyroid cancer
  • Gallbladder cancer (Lauby-Secretan et al., 2016)


Additional cancers, such as liver, ovarian, and multiple myeloma, may also have obesity-related risk factors (World Cancer Research Fund, 2018).


Evidence Connecting Obesity to Cancer

  • A National Cancer Institute (NCI) study using SEER data estimated that in 2007, 4% of new cancers in men (34,000 cases) and 7% in women (50,500 cases) were attributable to obesity (Polednak, 2008).
  • The proportion of obesity-related cancers varied by type, reaching 40% for endometrial cancer and esophageal adenocarcinoma (Arnold et al., 2016).


Projected Future Impact

  • If current obesity trends continue, the U.S. could see 500,000 additional cancer cases by 2030 (Tran et al., 2019).
  • Similar projections exist in Australia, where obesity is expected to become the leading preventable cause of cancer within decades (Australian Institute of Health and Welfare, 2021).


Reducing Obesity’s Cancer Burden

  • A 1% reduction in average BMI (about 1 kg of weight loss for an average adult) could prevent ~100,000 new cancer cases in the U.S. (Pearson-Stuttard et al., 2018).
  • Sustained weight loss, even modest (5–10% of body weight), significantly lowers cancer risk (Steele et al., 2019).


Why Does Obesity Increase Cancer Risk?

Multiple biological mechanisms explain the obesity-cancer link:

  1. Excess Estrogen Production
  2. Fat tissue increases estrogen levels, raising risks for breast, endometrial, and ovarian cancers (Key et al., 2020).


Hyperinsulinemia & Insulin Resistance

  • Elevated insulin and insulin-like growth factor-1 (IGF-1) promote tumor growth (Gallagher & LeRoith, 2021).


Adipokine Imbalance

  • Leptin (pro-cancer) rises with obesity, while adiponectin (anti-cancer) decreases (Park et al., 2020).


Chronic Inflammation

  • Obesity triggers low-grade inflammation, activating NF-kB and COX-2 pathways linked to cancer (Greten & Grivennikov, 2019).


Dysregulated Cell Signaling

  • Altered mTOR and AMPK pathways disrupt cell growth controls (Hopkins et al., 2020).


Oxidative Stress & Immune Suppression

  • Excess fat generates reactive oxygen species (ROS), damaging DNA and weakening immune surveillance (Bianchini et al., 2022).